The "close" price of this data point. It's acceptable to have null here
for a few data points, but they must not all be null. If either open or
close is null for a data point, it will appear as a gap in the chart.
The "open" price of this data point. It's acceptable to have null here for
a few data points, but they must not all be null. If either open or
close is null for a data point, it will appear as a gap in the chart.